The present invention relates to a device on a double disk lapping machine to bring an upper machining disk into its working position.
Double disk lapping machines have been known for about 40 to 50 years. Pieces to be machined are pulled between the two machining disks by so-called sliding disks with the aid of an inner and outer annulus of vertical pins, and are machined. With double disk lapping machines it is possible to achieve very great parallelism of the machined surfaces of the workpieces. Through the appearance of new technologies, such as the production of silicon disks for integrated circuits, the production of crystals or of the finest ceramic tiles, greater and greater demands have been made of lapping machines. Particularly in the machining of extremely thin-walled materials greatest attention is to be paid to the control of the working pressure of the upper machining disk of double disk lapping machines. Today machines are required in which the upper machining disk is conveyed to the working position as quickly as possible or immediately before the machining disk comes into contact with the surface of the workpiece to be machined. The placing of the upper machining disk on the surface of the workpiece should be done as finely as possible, however, practically without pressure. During machining of the workpieces the working pressure is, depending upon type of utilization, to be continuously controlled according to certain guidelines and to be reduced again at the end of machining in order to lift the machining disk off of the workpiece and to pivot it to the side so that the lapping machine is emptied.
In the design types of double disk lapping machines known today, the upper machining disk in most cases is hung on a motor drivable and axially movable spindle. The spindle is connected to a radially pivotable column of the lapping machine via a bearing component. Via a hydraulic or pneumatic cylinder drive, which connects to said axially movable spindle, the upper machining disk fixed on the lower end of the spindle can be conveyed to, placed upon, and pressed against the workpiece. The cylinder drive first has to compensate the weight of the up to several-thousand-Newton-heavy upper machining disk, bring the machining disk to the workpiece, place it on slowly as already described, and begin with the strain of reduction of weight compensation. On the one hand, since working pressures of some 10,000 Newton are required today, contact pressure conditions result which are hard to control if there is a changeover to an additional strain when removing the weight compensation of the upper machining disk through pressure reversal in the cylinder drive. On the other hand, in the modern-day machines the column tends to tilt with the radially designed upper machining disk as a result of the enormous working pressure. In both cases the precision of the work consequently suffers.
A further embodiment according to the German published application 35 20 713 A 1 tries to circumvent the difficulties mentioned in that the upper machining disk, situated on the lower end of a spindle with an axially movable bearing component, is hung on one end of a two-arm lever while the pneumatically operated adjusting devices are connected on the other end of the lever. This design is both mechanically and control technically extravagant.
It is the aim of the present invention to create a device on a double disk lapping machine in which said disadvantages of bringing the upper machining disk to, and pressing it against, the surface of the workpiece do not arise. In contrast to the known embodiments of double disk lapping machines, the machine equipped with the device according to the invention is of significantly simpler construction.
The invention fulfills this aim as a result of providing a column which is raisable and lowerable by means of a drivable lifting spindle. A mechanism for maintaining the beam in a substantially horizontal orientation is provided which acts to keep the beam horizontal when the column is lowered. A working pressure adjusting means is also provided between a holder arm, which is firmly connected to the column, and a rear beam end of the beam.